1. Field of the Invention
The present invention relates to a method of producing a semiconductor device or a photodetector device by adhering a plurality of semiconductor substrates in a planar manner, and more particularly to a method of producing a semiconductor device having a plurality of semiconductor elements over a large area, a one- or two-dimensional image reading device adapted for use in a facsimile, a digital copying apparatus or a scanner, and a photodetector device for converting a radiation such as X-ray or gamma-ray into visible light or the like by a fluorescent plate and reading thus converted light.
2. Related Background Art
The amorphous silicon (hereinafter abbreviated as "a-Si") has been conventionally utilized as the semiconductor material for a large-area semiconductor device or as the photoelectric converting semiconductor material for a photodetecting device such as a sensor array. In particular, such film can be easily formed on a large-area glass plate and further it can be used not only as the photoelectric converting material but also as the semiconductor material for the switching TFT (thin film transistor). It is also widely employed as the semiconductor material for the sensor array, since the semiconductor layer of the photoelectric converting elements and the semiconductor layer of the switching TFT can be simultaneously formed.
As a typical example of the sensor array employing such a-Si film, there will be explained the constitution of a sensor array in which a PIN type photoelectric converting element is combined with an inverse staggered TFT constituting a switching TFT as a part of the control unit.
FIG. 1 is a schematic plan view of such a sensor array. In FIG. 1, numeral 101 indicates a PIN type photosensor; 102 a switching TFT; 103 a data line; 104 a gate line; and 105 a bias line. Each pixel is composed of a sensor portion and a switching TFT portion, wherein each photosensor is connected to each switching TFT which is connected to the data line 103.
FIG. 2 is a schematic cross-sectional view of one of the pixels shown in FIG. 1. In FIG. 2, numeral 101 indicates a PIN type photosensor; 102 a switching TFT; 201 a glass substrate; 202 a Cr gate electrode; 203 a SiN (silicon nitride) gate insulation film; 204 an i-type a-Si film; 205 a SiN channel protective film; 206 an n.sup.+ -type a-Si film; 207 an Al S-D electrode; 210, 211, 212 p-, i- and n-type a-Si films, respectively; 208 a Cr electrode; 209 an ITO electrode; 213 a SiN interlayer insulation film; and 214 a protective film.
In the following there will be briefly explained a radiation image pickup device as an example of the photodetector device utilizing the above-described sensor array substrate. FIG. 3 shows a schematic cross-sectional view of the structure of such a device.
As shown in FIG. 3, the radiation image pickup device is composed, for example, of a sensor array 301; a base member 308 serving to support the sensor array and to function as a shield against the radiation; an adhesive 309 for connecting the sensor array 301 and the base member 308; a fluorescent member 302 functioning as a wavelength converting member for converting the radiation into light to which the sensor array is sensitive; a processing circuit board 303 for processing electrical signals obtained from the sensor array; an IC 307 for driving the sensor array and the processing circuit; and a flexible wiring 304 for connecting the processing circuit board with the sensor array. These components are fixed by a frame 305 constituting the outer frame of the radiation image pickup device. The radiation enters from a direction indicated by an arrow 310. Such structure realizes a light and thin radiation image pickup device of a large size.
Lower cost, higher performance and larger area are currently being demanded for such photodetector devices, but such demands have not been met because of various problems which are yet to be solved. These problems will be explained in the following.
Firstly, for realizing a larger area, particularly a size in excess of 400.times.400 mm, there are required a capital investment on the large-sized manufacturing facility for matching the large substrate size and automation of each equipment constituting such facility and the substrate transportation therein. This leads to an increase in the product cost.
Secondly, in case of producing a large array substrate such as the two-dimensional sensor, the increase of the substrate size results in the decrease of a manufacturing yield, leading to the increase of the product cost.
Thirdly, the increase of the area deteriorates the uniformity of device properties, and the uneven distribution of the properties within the panel (substrate) deteriorates the product quality.
Though these problems are associated with the increase of size, there is desired a large-sized semiconductor device or photodetector device of a lower cost and a higher performance.